Soil physicochemical characteristics and bacterial community across two geological formations in Ciletuh-Palabuhanratu UNESCO Global Geopark, Indonesia

The Ciletuh–Palabuhanratu UNESCO Global Geopark in West Java, Indonesia, is recognized for its exceptional geological diversity; however, information on how contrasting geological formations influence soil physicochemical properties and bacterial communities remains limited. This study compared soil physicochemical characteristics and bacterial community composition between the Ciletuh Formation in Cibanteng Nature Reserve (CNR) and the Cikarang Member of the Jampang Formation in Cipeucang Conservation Forest (CCF). Twenty plot-level composite soil samples were collected from each geological formation for physicochemical analyses, while one representative composite sample from each formation was subjected to 16S rRNA gene amplicon sequencing. CNR soils were characterized by predominantly sandy texture and lower pH, whereas CCF soils contained higher proportions of silt and clay together with significantly greater total phosphorus and total potassium contents. Principal component analysis clearly distinguished the two geological formations based on their soil physicochemical properties. Amplicon sequencing generated 651 amplicon sequence variants (ASVs), revealing distinct bacterial community compositions. Actinobacteriota, Proteobacteria, and Chloroflexi predominated in CNR, whereas Proteobacteria, Actinobacteriota, and Methylomirabilota predominated in CCF. These findings demonstrate that contrasting geological parent materials are associated with distinct soil physicochemical environments and bacterial communities, providing the first baseline assessment of geology–soil–microbiome relationships in the Ciletuh–Palabuhanratu UNESCO Global Geopark.